The durability of surgical bypass and endarterectomy for arterial occlusive disease is often limited by the process of intimal hyperplasia which forms as a result of the accumulation of smooth muscle cells (SMC) and matrix proteins in the subintimal space of the surgical bypass or the reconstructed vessel. Since few SMC reside in the intima of human vessels, migration of SMC from the media to the subintimal space is an essential step in the formation of hyperplastic plaque. Although various growth factors and matrix proteins have been shown to influence SMC migration, the intracellular events that accompany migration and the signaling pathways that are activated by these factors are incompletely understood. The goal of this proposal is to gain a broader understanding of the characteristics of migrating human SMC and to describe the intracellular signalling pathways that are necessary for migration to occur. Prelimiary studies reveal that several intracellular events accompany SMC migration, including changes in the organization of filamentous actin and activation of a series of proteins that appear to act as links between signaling pathways and the cytoskeleton. We have also identified three second messengers systems that exert significant control over the process of migration. To further characterize SMC migration and delineate the intracellular events associated with this process, this proposal will: (1) Assess the influence of growth factors and matrix proteins on cellular morphology, organization of f-actin, activation of cytoskeletal proteins, and migration of vascular smooth muscle cells. (2) Evaluate the role of protein kinase C activation in SMC migration and determine which isotype(s) of PKC are responsible for this effect. (3) Evaluate whether changes in total cellular Ca2+ or changes in the intracellular distribution of Ca2 + are necessary for SMC migration. (4) Evaluate the importance of the small GTP-binding protein rho in activation of cytoskeletal proteins and SMC migration and determine the upstream and down stream pathways necessary for the effect of rho. We expect that the studies outlined in this proposal will expand our knowledge of the pathophysiology of intimal hyperplasia and also further our understanding of the basic physiology of cellular migration (a process that is necessary for a number of physiologic as well as pathologic events). The intracellular events and signaling pathways that will be described may eventually serve as selective targets for inhibitors of intimal hyperplasia. Since intimal hyperplasia leads to failure of a significant percentage of vascular rcconstructions, and since SMC migration is an important and essential feature of this process, we feel that the studies outlined in this proposal will provide useful information that will have an impact on our understanding of an important disease process.